Implementing a bridging-level firewall
The Drawbridge
Firewalls are typically implemented as routers,but it doesn’t have to be that way. Bridging packet filters have a number of advantages,and you can add them to your network at a later stage without changing the configuration of your network components.
Linux has earned a reputation as an excellent firewall platform. The kernel has a powerful Netfilter/ IPtables-based packet filter. In a traditional firewall scenario, Netfilter resides on a router, where it subdivides the network into two or more subnets. But adding a firewall to an established network can involve changing the network infrastructure. This effort can result in IP address changes and modifications to access controls for internal services. It is far simpler to add a bridge. Bridges reside in layer 2 of the OSI reference model and normally inspect MAC addresses rather than IP addresses (see the box titled “Building Bridges”). Linux can leverage this capability in a clever way to add transparent firewalling to a network. Of course, the bridge evaluates packets from the higher protocol layers (IP addresses, TCP ports) in its role as a firewall. But the hosts on the network will not notice a thing, unless they attempt to send illegal packets.
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
![Learn More](https://www.linux-magazine.com/var/linux_magazin/storage/images/media/linux-magazine-eng-us/images/misc/learn-more/834592-1-eng-US/Learn-More_medium.png)
News
-
NVIDIA Released Driver for Upcoming NVIDIA 560 GPU for Linux
Not only has NVIDIA released the driver for its upcoming CPU series, it's the first release that defaults to using open-source GPU kernel modules.
-
OpenMandriva Lx 24.07 Released
If you’re into rolling release Linux distributions, OpenMandriva ROME has a new snapshot with a new kernel.
-
Kernel 6.10 Available for General Usage
Linus Torvalds has released the 6.10 kernel and it includes significant performance increases for Intel Core hybrid systems and more.
-
TUXEDO Computers Releases InfinityBook Pro 14 Gen9 Laptop
Sporting either AMD or Intel CPUs, the TUXEDO InfinityBook Pro 14 is an extremely compact, lightweight, sturdy powerhouse.
-
Google Extends Support for Linux Kernels Used for Android
Because the LTS Linux kernel releases are so important to Android, Google has decided to extend the support period beyond that offered by the kernel development team.
-
Linux Mint 22 Stable Delayed
If you're anxious about getting your hands on the stable release of Linux Mint 22, it looks as if you're going to have to wait a bit longer.
-
Nitrux 3.5.1 Available for Install
The latest version of the immutable, systemd-free distribution includes an updated kernel and NVIDIA driver.
-
Debian 12.6 Released with Plenty of Bug Fixes and Updates
The sixth update to Debian "Bookworm" is all about security mitigations and making adjustments for some "serious problems."
-
Canonical Offers 12-Year LTS for Open Source Docker Images
Canonical is expanding its LTS offering to reach beyond the DEB packages with a new distro-less Docker image.
-
Plasma Desktop 6.1 Released with Several Enhancements
If you're a fan of Plasma Desktop, you should be excited about this new point release.